Metallic denture backing



July 31, 1923.-

R. M. CRAIG METALLIC DENTURE BACKING Filed June 27, 1919 INVENTDR.

:l TTORNEY.

Patented July 33, 1923 TNT ROBERT M. snare, or WILKINSBURG, PENNSYLVANIA.

' METALLIC DENTURE BACKING.

Application filed June 27, 1919.

To all whom it may concern: I Be it known that I, Ronnn'r MnADn CRAIG, a citizen of the United States, residing at VVilkinsburg, in the county of Allegheny.

and State of Pennsylvania, have invented a certain new and useful Improvement in Metallic Denture Backings, whereof the following is a specification, referencebeing had to the accompanying drawing.

My improvement relates to a metallic backing for a porcelain tooth facing, which may be utilized in a plate, bridge, or other form ofdenture, and of the class contemplated in Letters Patent 12,753 reissued to me February 18, 1908.

Letters Patent of the United States 1,221,420, granted to me April 8, .1917, with claims for such a backing comprising a pair of opposed and oppositely counterpart members, spaced and arranged to embrace the porcelain body hetween them and united by a fusible element between them. I found it convenient to make those members of cast metal, and such construction is advantageous in that such members of a single size may be used to form metallic backings of different sizes, by interposing more or less of the fusible element between them. However, that method of manufacture requires a great deal of-time and skilled labor, and it is the object of my present invention to provide a backing structure which is susceptible of quantity production with the minimum amount of labor, by a method and means which form the subject matter of other applications for Letters Patent of the United States copending herewith. Said method is claimed in application Serial 305,- 421 filed June 19, 1919, and said means include metal drawing dies claimed, in application Serial 305,4122, filedJune 19, 1919, and pressing mechanism claimed in application Serial 308,590 filed July 3, 1919.

In accordancevwith that method, a primarily plane strip of sheet gold, of. uniform thickness, is drawn'through suitable dies to form an 'I-bar, having opposite faces of substantially cylindriform curvature, so that the opposite longitudinal edges of said bar are about twice as thick as the throughout its length. Saidbar' is then divided to form a plurality of backing blanks, by snnilar successive punching operations each of which produces a single blank, of approx- Serial No. 307,104.

imately rhombic configuration, the shorter axis of which coincides with the longitudinal axis of said bar. Each of said blanks is then pressed, in suitable dies, so as to turn its thick edges upward, in substantially par allel relation, so that it is U shaped invcross section, considered transversely with respect to theoriginal bar, although arched at its intermediate portion in the direction of the length of said bar, to form the metallic denture backing which I desire to claim herein.

My improved. backing, formed as above described, difi'ers from thatshown in my Letters Patent 1,221,420 aforesaid not only in that it is formed of a single piece of metal, instead of being formed of three pieces; but also in that the web thereof intermediate of its side flanges is of uniform cross section throughout its length and thinner at its medial longitudinal axis than-at its opposite edges. .It may be observed that, such differences connotea material saving in gold, as the result of employment of .my present invention, in comparison with-the form of backing shown in said Letters Pat'- ent 1,221,d20, in which the intermediate web was not only of irregular cross section throughout its length but of considerable thickness to engage. the fusible element.

In other words; my present invention is advantageous, as compared with that shown in said Letters Patent, not only in providing a metallic backing of the specific class backing blank punched from said I-b'ar.

Fig 111 is a perspective view of the U- shaped backing pressed from said blank.

Fig. IV is a central longitudinal sectional view of said backing; showing the uniform thickness and arched configuration of its central web.

Fig. V is a plan view of said backing embodied in a denture representing a bioupsid tooth, showing that, although substantially U-shaped in cross section, its flanges'are closer together at their free edges than at their'junctions withsaid web so as to form an undercut recess to receive the porcelain tooth facing of said; denture.

Fig. VI is a front elevation of said bicuspid denture.

Fig. VII is a left side elevation of said bicuspid denture.

Fig. VIII is a rear elevation of said bicuse pid denture. Referring to Fig. I; the I-bar aforesaid has its opposite faces substantially cylindriformly curved throughout its length, so as to form a thin web 1 with opposite thick longitudinal edges 2, of the same transverse cross section, throughout its length. Such a bar is preferably formed of gold, but may be formed of any other suitable metal or alloy.

Referring to Fig. II; it may be observed that the backing blank 3, which is conveniently formed from said bar by a punching operation, is of approximately rhombic outline, having its axis 4t corresponding with the longitudinal axis of said bar. It isto be noted that the shape of said blank is such that the major portion ofits area is formed of the thinner portions of said bar; only a fraction of said area being formed of the thickest, edge portions, of said bar.

Referringto Fig. III; it may be observed that the substantially U-shaped metallic backing, formed from said blank 3, has opposite side flanges formed, by the thick edges 2 aforesaid bent so that they converge both from the bottom toward the top, and from the thin intermediate web 1 toward the observer. Although said side fianges merge into said web directly at the upper edge of the latter; they merge into said web above the lower edge of the latter so as to leave a downwardly projecting portion 5, which, as hereinafter described, forms a locking flange for engagement with the porcelain facing to prevent the accidental escape. of the latter from said backing; although said flange may be returned to the position shown in Figs. III and IV to permit said facing to be removed at any time. Fig. IV shows the arched configuration to which the thin web of said backing is bent from the straight initial form of the bar shown in Fig. I, and alsoshows the uniform thickness of said web throughout the length of said backing.

Referring to Figs. V to VIII inclusive; the. porcelain body comprises. the anterior portion 7; and the posterior portion 8 in unitary relation. Said anterior portion forms a. facing which may be of any desired size, representing a natural tooth, and said posterior portion forms a dovetail 9 whereby saidbody is supported in and engaged by said metallic backing 10, which may form part of a plate, bridge, or other denture. As indicated by the dotted lines in Figs. V, VI

and VIII; said dovetail 9 is, wedge shaped in two directions at right angles to each othor, its side faces convergingboth from its occlusal end 11 to its gingival end 12 and from its lingual side 13 to its labial or buccal side 14*, where it merges into the anterior portion 7 of said body; said converging surfaces being symmetrically disposed with respect to the central vertical plane of the porcelain body. Saidposterior dovetail por tion 9 is also converged and eoncavely curved longitudinally in its lingual face, from its gingival end toward its occl usal end, as best shown at 9 in Fig. VII. Said posterior por tion 9 of; said porcelain body being thus converged in three directions, as above described, is fitted in the correspondingly shaped recess in said metallicbacking- 10, the exterior contour 14: of which resembles that of the tooth imitated; by the anterior portion 7 of said porcelain body.

It is to be noted that the construction and arrangement above described are such that the strains to which the denture is normally subjected, viz, pressure in a direction from its occlusal; or incisal end toward its gingival end, and transversely from its lingual to its labial side, merely serve to more firmly seat said porcelain body in its backing 10. Although there is nonormal; strain upon the denture tending to remove said porcelain body from its metallic backing in the direction from its gingi-val end tov its. occlusal end, it may be manually slid: and re moved in that direction, Withoutremoving the backing from its setting, whenever it is desired to remove the porcelain body. Therefore, although it is unnecessary topror vide any special means; for preventing-such sliding movement in addition to the frictional engagementbetween said? body and its backing, they may be cemented in connection with each other, and I prefer tov pro vide said backing 10 with the unitary looking flange 5 which, when bent as indicated in dotted lines in Fig. IV and inf-ull lines in Fig. VII, normally prevents said porcelain body from. thus sliding, so-that it isnecess sary to straighten said flange 5 to the position shown in full lines in Fig. IV and in dotted lines in Fig. VII, to remove said body. Said locking flange 5 maybe rebent to engage the porcelain bodywhen it is.r.eplaced in said backing 10.

@f course, my present invention also differs from that claimed; in said Letter Patent 1,221,420, in that it isnecessary to have dies of respectively different sizes: corresponding, with different sizes of'natural teeth, to formthe blanks shown: in Fig. II and bend them as exemplified in; Fig. III. However, the cost 011 such diesis negligible as compared with the great saving i'n. cost of manufacture above contemplated; A; single bar, such as shown in Fig.- I, may; be, of

such size and proportions that it may be used for all sizes of blanks required. All

sizes of porcelain bodies for a given tooth may be conveniently recessed alike, to receive the side flanges of metallic backings 10 such as above described; so that the dies for forming the different sizes of the latter may be all of one pattern, for a given tooth, except that they are of respectively difierent Widths.

Therefore, I do not desire to limit myself to the precise details of construction and arrangement herein setforth, as it is obvious that various modifications may be made therein Without departing from the essential features of my invention, as defined in the appended claims.

I claim:

1. A metallic denture backing comprising a single piece of pressed sheet metal of uniform thickness in parallel planes but of greater thickness at its opposite edges than intermediate thereof, and having a bendable locking flange intermediate of said edges.

2. A metallic denture backing comprising a single piece of pressed sheet metal of uniform thickness in parallel planes but of greater thickness at its opposite edge than intermediate thereof.

3. A metallic denture backing having a thin middle part and thickened projections at opposite edges extending to said middle part only.

In testimony whereof, I have hereunto signed my name at Wilkinsburg, Pennsylvania, this sixth da of November, 1918.

KOBERT M. CRAIG. Witnesses: I

R. A. COLEMAN, H. R. CRAIG. 

